Film-forming compositions for oilproof containers



Feb; 10, 1948.

V. V. VALLANDIGHAM FILII-FORI ING COMPOSITIONS FOR OIL-PROOF CONTAINERSHEAVY BODIED MODIFIED ALGIN HIGH VISGOSITY ALGIN HIGH IN A ACCE LE RATORMODIFIED ALGIN HIGH IN HUMECTANT LOWVVISCOSITY ALGIN man In ACCELERATORLOW IN HUMEOTANT' Fil ed Dec. 27, 1943 LHBEL l III \LWALLAN DIGHAMINVENTOI Patented Feb. 10, 1948 I FILM-FORMING COMPOSITIONS FOR OIL-PROOF CONTAINERS Vance V. Vallandigham, Park Ridge, Ill., winner toKelco Company, San Diego, Calif., a corporation of Delaware ApplicationDecember 2'1, 1943, Serial No. 515,839

8 (Illaims. (Cl. 106-162) This invention pertains to the preparation ofcompositions, consisting primarily of algins, which on spreading anddrying yield oil-proof, highly adhesive and flexible films, and to theuse of such compositions in the manufacture of laminated papers and ofpaper containers for oils and greases.

A purpose of the invention is to provide means for working paper stockinto containers which are wholly proof against leakage of or staining byoleaginous contents and which maintain the oil-proof characteristicthrough extended storage of the filled container and also when it issubjected to rough handling.

A purpose of the invention is to provide materials for producing alaminated paper which is at once highly flexible and completely andpermanently grease-proof and which may be used for wrapping cheese,butter and other oily or greasy products.

A purpose of the invention is to so modify the normal characteristics ofan algin film as to improve its stability and to cause it to remainflexiing or flooding with the described coating com-- ble for anindefinite period, even under conditions of varying humidity.

A purpose of the invention is to so modify the normal characteristics ofan algin film as materially to increase its adhesive property and tocause this property to develop rapidly after spreading.

The paper containers to which the invention most specifically appliesare of two general types: cylindrical and rectangular. The first namedare generally used for liquids and soft or semi-solids, as for example,lubricating oils and greases. ointments and the like. Such solids ascheese, butter and oleomargarine are more often placed in rectangular,folded containers.

Cylindrical containers are made, in general terms, by forming on a shaftor mandrel a tube consisting of a plurality of plies of suitable paper,wound in spiral or convolute form and cemented together as wound. Thistube is cut into'lengths and paper or metal caps applied to close theends. Paper caps are desirably used for relatively light materials andfor small packages. Such heavy liquids as mixed paints may require metalcaps, which are preferably applied with a special composition (seeExample 6).

The attached drawing illustrates, in elevation and partial section, athree-ply cylindrical container made up with the compositions hereindescribed, the thicknesses of the various layers being grosslyexaggerated.

Rectangular containers may be made by folding laminated or previouslycoated paper or cardboard into the desired form and cementing the laps.They may also be made by folding up and cementing single-ply, uncoatedpaper and spraypositions.

Either the cylindrical or the rectangular form may have a surfacecoating of one of the compositions applied either inside or outside, orboth, though such coatings are more often given to cylindrical than torectangular containers. Either type may have a label or labels afllxedbefore or after scaling, for which purpose a specific modification ofthe invention is provided (see Example 3).

-These methods of manufacture are well known and understood. They arementioned here only because the different situations in which thecompositions of the invention are used require the development ofdifferent properties or, more accurately, of the characteristicproperties in different degrees.

The basic requirements in a composition adapted to the manufacture of anoil-proof paper package are as follows:

1. The composition must spread readily and form a homogeneous andconsistent film, free from imperfections;

2. The film so formed, when dried to equilib-- rium with the atmosphere,must be wholly unaffected by contact with oils or fats, and impenetrabletoward such substances;

3. The oil-proof pellicle formed by such drying must be strongly bondedto the adjacent paper surface or surfaces: i. e., the composition mustbe strongly adhesive; 4. The adhesive property or so-called tack, whichis substantially absent fromthe freshly spread film, must develop asrapidly as possible, by evaporation, on exposure of the film to the air:this characteristic is particularly important in the use of thecomposition for cementing tube plies, as it largely determines the speedat which the machine may be operated;

5. The dried pellicle must be to the greatest degree flexible in orderto resist cracking when the sheet is folded or the package is deformedby rough handling;

6. The pellicle must come to equilibrium with even dry air at suchdegreeof hydration as fully to retain its flexibility: it must not dryout and thereby become brittle.

' terial, which yields the oil-proof pellicle; an adhesion accelerator,and a humectant, together with water as a solvent and vehicle.

As film-forming agents, some of the alginates have an unique value. Thisis due primarily to their colloidal state, which causes them to fllterout of the aqueous vehicle and form a pellicle 0n the surface Of anabsorptive material such as paper. As these substances do not penetratethe fibrous sheet to any material extent, a consistcut and imperviousfilm may be very thin, and thus a small quantity of this moderatelycostly substance covers a relatively large surface. The pellicle, evenwhen very thin, is to the last degree oil-reslstant and, if maintainedin a suitable state of hydration, is extremely flexible and diflicult torupture by handling or folding of the sheet on which it is deposited.

The prior art has recognized these advantages in describing the use ofvarious alginates for the coating of paper and the lining of papercontainers. But as such applications have not come into commercial useit would appear that the prior art did not recognize the inherentdefects of the alginates. These defects, which are suflicient to destroythe utility of the unmodified alginates for these purposes, are: theslowness with which the freshly prepared film becomes tacky; the lack ofsufiicient bond between the pellicle and the paper surface on which itis spread, which in turn is due to the lack of penetration of thealginate into the capillaries of the paper, and the marked tendency oftheunmodified alginate to' dry out and become brittle.

The adhesion accelerator, of which glucose is an example, remedies thefirst of these defects by rapidly developing sufiicient tack to provideinitial adhesion, thus speeding up all cementing operations. It remediesthe second defect by penetrating the fibre of the paper and thusproviding the otherwise lacking bond between the alginate pellicle andthe surface or surfaces of paper on which it is formed.

The humectant, of which sorbitol is an example, remedies the thirddefect by retaining in the pellicle sufiicient water to render itpermanently flexible. It also ofisets a tendency, which may otherwisedevelop, toward crystallization of the adhesion accelerator in thepellicle and the consequent disturbance of the continuity of theoil-proof film.

Not all the alginates are suited to this use, only those which arefreely water-soluble being available. Of the soluble compounds, thedouble salts or complexes of alginic acid with ammonia or amines and theheavy metals are barred by rea son of their poor film-forming qualityand, in most cases, by toxicity which renders them incompatible with anyedible product. The amine and alkylolamine salts are functional butundesirable, partly by reason of their relatively high cost without anycompensating advantage, partly because they cannot be prepared andshipped in the dry form.

The algins contemplated for the purpose of this invention are thereforelimited (with the ex-- ception just made) to the salts of alginic acidwith sodium and potassium (and the rare alkali metals which, again, areimpracticable because of their cost) and with ammonium and magnesium.The sodium salt is preferred as being the least expensive and fullyfunctional.

The viscosity of algin solutions of equal concentration varies over awide range, depending on the method of manufacture and the extent towhich the extremely large molecule of the alginic acid has beendepolymerized in separating it from the algae in which it originates. Itis preferable to use an algin having a moderately low viscosity. as forexample a grade having a McMichael viscosity of 7500 centipolses in 4%aqueous solution. It is possible, however, to use algins having4%viscosities ranging from about 250 centipoises to about 600 poises,controlling the viscosity of the composition as prepared for use by varyng the d iii) gree of dilution. The range of viscosity here given isintended to be suggestive, not limiting, as algins outside thisviscosity range may be employed for special purposes.

The specific viscosity of the algin used should be selected with a viewto balancing the spreading property against film impenetrability. Inorder to spread readily by the methods currently used-brushing,spraying, glue-pot or doctor blade-the composition as diluted for useshould have a mucilaginous consistency. For the coating of containers bybathing and draining a. thinner dilution may be advisable. Suchconsistency as is required by the particular operation may be obtainedby the use of a high viscosity algin, highly diluted, or of an algin oflower viscosity in greater concentration.

The first alternative is economical of algin, less of the solid beingrequired to produce any desired spreading consistency. 0n the otherhand, a thinner film is formed and, if dilution be carried too far, thealgin will penetrate into the fibre of the paper instead of remaining onits surface and the film may lack tightness or may not be formed.

The second alternative yields a relatively thick dried pellicle, whichis more certain to be oiltight, but if the specific viscosity of thealgin be too low and the concentration correspondingly high, theconsumption of the most expensive ingredient of the composition will beexcessive. The technical advantage, therefore, lies with the use of arelatively large quantity of a low viscosity algin, the economicadvantage with the substitution of a smaller quantity of an algin ofhigh specific viscosity.

It will be borne in mind, in consideringthe practical formulae given inthe examples below, that the relatively small proportion of algin is thesole film-forming ingredient, and also the component which impartssubstantially all the observed viscosity to the liquid composition andthe oil-proof character to the dried film. The film thickness and thespreading properties of the composition are therefore governed, not bythe weight relation of algin to other solids, but rather by the relationof algin to water; i. e., on the concentration of algin in the solutionand on the specific viscosity of the algin. The adhesion accelerator andthe humectant, while they strongly modify the characteristics of thealgin pellicle, have only a slight effect on the thickness of the filmor on those properties of the composition which affect its application.

In lieu of glucose as an adhesion accelerator one may use another sugarsuch as sucrose, dextrose or levulose, or a solubllized starch such asdextrin or amylodextrin. The glues and gelatines are not suitablesubstitutes in spite of the strong adhesiveness which some of themdevelop. In using any of these substances the equivalent weight is abouteight-tenths that required in the use of an glucose.

In lieu of sorbitol as the humectant one may use any of the polyhydricalcohols, such as glycerine or one of the glycols. It is preferable touse sorbitol or other humectant having an inherent humidity range, inspite of a possibly larger quantity required, as in the use of thealcohols the dosage must be carefully limited to avoid excessivehygroscopicity of the pellicle. This is particularly important incompositions used for exterior coatings, in which an excessive use ofethylene glycol or glycerol may render the composition permanentlysticky.

It will be remembered that the purpose or the hume'ct'ant is not toimpart plasticity, per se', but rather to retain in the algin film thatsmall but very necessary proportion of water by which the algin ismaintained in a plastic and flexible condition.

The proportions in which the above components maybe used areillustrated, but not limited, in the following examples of compositionswhich have been used with success-in the large scale manufacture ofcylindrical containers, ranging in size'from one ounce to five gallonscapacity. The algin used throughout hada McMichael viscosity in 4%aqueous solution of 7500 centipoises' an the proportions given are byweight.

Example 1 Sodium alginate parts-.' 8 Glucose ....do -J 46 Sorbitol do 46Water do 100 Concentration algin in waterper cent 8 Ratio algin to totalsolids l:12.5 Ratio algin to accelerator 1: 5.7 Ratio algin to'hurnectant l: 5."! Ratio accelerator to humectant 1': 1.0

This example yields an all-purpose product generally adapted to theoperations connected with manufacture of oil-proof cartons of differenttypes, but is not so economical for some specific uses as other formulaegiven below. It affords a relatively thick and completely oil-proofpellicle with ahigh degree of stability, but develops its initialadhesion more slowly than thecomposition This product is specificallyadapted to cementing the plies of paper tubes from which cylindricalcontainers are formed. The concentration of algin is high enough to givea relatively thick bonding and oil-proofing pellicle. The develop-' mentof adhesion is promoted by'largely increasing the proportion ofaccelerator at the expense of the humectant. Because of the protectionatforded by the superimposition of plies, the requirement for humectantis at the minimum.

Example 3 Sodium alginate parts 4 Glucose do..-- 88 Borbitol e do.. 8Water ..do 100 Concentration of algin in-water-..-per cent... 4 Ratioalgin to total solids-.. 1:250

Ratio algin to accelerator 1522.0 Ratio algin to humectant 1: 2.0 Ratioaccelerator to humectant ii: 1.0

This is the same formula as in Example 2 but with double the quantity ofwater to'reduce viscosity and facilitate :brush spreading. The adhesioncharacteristic is exaggerated and the product is particularly adapted tothe labelling of containers, either before or after filling.

. Example 4 Sodium alginate--..-'. .-..".parts 7 Glucose .do.. "-v 78Sorbitol .'.:...do 18 Water do--.*.' 167 Concentration algin inW&t6l'..'..'.j-P!";C0lll-l 4.2 Ratio algin to total solids 91:14.3 Ratioalgin-to accelerator -l":ll.l Ratio algin to 'humectant 1:2.1 Ratioaccelerator; to humectant -4 5.2:l.0

l'xample 5 Sodium alginate. -.parts.; 4 Giueos'e do.-:i 98 Water -e.'--do..-;-; 100 Concentration algin in water-..--per cent.; 4 Ratioalginto accelerator 1224.0

This is a very iree spreadingproductadapted solely to the labelling ofmau packages which are otherwise. oil-prooied. It is strictly :an adhesive, of very high. grade, and should not be used for. oil-proofingbecause of the lack of per maneht flexibility which follows the omissionorv the hllme'dtant.

Example 6 Sodium alginate ...'parts.-. 4 Glucose l do '17 So'rbitol..-..do; 10 Water ...'--do .i. 80 Concentration algin in 'water -per:'cent.'-6.! Ratio algintototalisolids 17:25.0 Ratio algin to'accelerator .-.l11119.2 Ratio algin to humectax'itl "124.7 Ratio accelerator tohumectant 4:1.0

- .This; is a, heavy bodied composition-adapted specifically tocementinghaps onto cylindrical containers.

To each or the above iormulaeit-is desirable to adds, minute amount of anontozric and odorleiis preservative such as .n -butyl-phydroxybenzolite at a concentration otabout 0.05% by;.wei'ght or thecomposition, This additionhas no other effect on thepropertles of thecomposition than to prevent-"fermentation of. the carbohydrates presentin it.

g It is also desirable, though by no. means lessen tial, to include. inthe composition a small-mo portion of a water-soluble salt ofphosphoric-acid,

as for. example trisodium phosphate orsodium hexametaphosphat'e (Calgon)The dosage may be-ot the.order oi' 1%.of the dry'weight-soi thecomposition.; The phosphates inhibit precipita tl'o'n 'of' insoluble:calcium alginateqvhen-hard waters are used for dilution. They also,iii-some cases. improve the-spreading qualities of the composition,particularly where its viscosity is high and it is consideredundesirable to reduce the viscosity by further dilution.

It. is impossible to fix any-absolute limits to the dosage of anycomponent of the composition. for the reason that some part of thebenefit of each component will be realized from even the smallestdosage. But experience has indicated that the ranges of practicalutility in the relation oi each component to the other are about asfollows:

Concentration of algin in water vehicle -per cent .'From 2 to In themaking of oil-proof papers, two or more sheets of relatively thin paperare cemented together by interposed films-of the composition, and mayfurther be coated on one side or both sides of the assembly. Thelaminated paper thus produced has a very high tensile strength and whenproduced in suitable thicknesses is highly adapted to the making ofcartons.

If the carton is additionally to be water-proofed on the outside, theoil-proof coating should be omitted from one side of the laminatedsheet.

I claim as my invention:

1. A film-forming composition for use in the manufacture of oil-proofcontainers from paper, consisting substantially of: an algin selectedfrom the group consisting of the alginates of the alkali metals,magnesium and ammonium; an adhesion accelerator selected from the groupconsisting of the sugars and the solubilized starches; a humectantselected from the group consisting of the polyhydric alcohols, and wateras a vehicle, in which the weight relation oi said algin to saidadhesion accelerator is within the range from about 1:5 to about 1:30.

2. A film-forming composition for use in the manufacture of oil-proofcontainers from paper, consisting substantially of an algin selectedfrom the group consisting of the alginates of the alkali metals,magnesium and ammonium; an adhesion accelerator selected from the groupconsisting of the sugars and the solubilized starches; a humectantconsisting of sorbitol, and water as a vehicle, in which the weightrelation of said algin to said sorbitol is within the range from about1:1 to about 1:6.

3. A film-forming composition for use in the manufacture of oil-proofcontainers from paper, consisting substantially of: an algin selectedfrom the group consisting of the alginates of the aikali metals,magnesium and ammonium; an adhesion accelerator selected from the groupconsisting of the sugars and the solubilized starches; a humectantselected from the group consisting of the 'poiyhydric alcohols, andwater as a vehicle, in which the weight relation of said algin to saidhumectant is within the range from about 2.5:1 to about 1:2.5.

4. A film-forming composition for use in the manufacture, of oil-proofcontainers from paper when dispersed in water as a vehicle, consistingsubstantially at: an algin selected from the group consisting of thealginates of the alkali metals. magnesium and ammonium; an adhesionaccelerator selected from the group consisting or the sugars and thsolubilized starches, and a humectant selected from the group consistingof the polyhydric alcohols, in which the weight relation of said alginto said adhesion accelerator is within the range from about 1:5 to about1:30.

5. A film-forming composition for use in the manufacture of oil-proofcontainers from paper when dispersed in water as a vehicle, consistingsubstantially of: an algin selected from the group consisting of thalginates of the alkali metals, magnesium and ammonium; an adhesionaccelerator selected from the group consisting of the sugars and thesolubilized starches, and a humectant consisting of sorbitol, in whichthe weight relation of said align to said sorbitol is within the rangefrom about 1:1 to about 1:8.

6. A film-forming composition for use in the manufacture of oil-proofcontainers from paper when dispersed in water as a vehicle, consistingsubstantially of: an algin selected from the group consisting of thealginates of the alkali metals, magnesium and ammonium; an adhesionaccelerator selected from the group consisting of the sugars and thesolubilized starches, and a humectant selected from the group consistingof the polyhydric alcohols, in which the weight relation of said alignto said humectant is within the range from about 2.5:1 to about 1:2.5.

7. A sealing composition adapted for attaching caps to cylindricalcontainers when brought to the consistency of a viscous liquid withwater, consisting of about 4 parts of an algin selected from the groupconsisting of the alginates of the alkali metals, magesium and ammonium,about 20 parts of glucose and about 5 parts of sorbitol.

8. A sealing composition for attaching caps to cylindrical containersconsisting of about 4 parts of an algin selected from the groupconsisting of the alginates of the alkali metals, magnesium andammonium, about 20 parts of glucose and about 5 parts of sorbitol, withwater suflicient to bring said components to the consistency of aviscous fluid.

VANCE V. VALLANDIGHAM.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

